The difference between air compressor soft starter and frequency converter
The soft starter is actually a motor control device with motor soft start, soft stop, light load energy saving and multiple protection functions. It is mainly the three-phase parallel thyristor and its electronic control circuit connected in series between the power supply and the controlled motor. By controlling the conduction angle of the three-phase parallel thyristor, the input voltage of the controlled motor can be changed according to different requirements, and various functions can be realized. Inverter, it is mainly used in places where speed regulation is required. Its output not only changes the voltage but also changes the frequency at the same time; the soft starter is actually a voltage regulator. When the motor is started, the output only changes the voltage and does not change the frequency. The frequency converter has all the functions of a soft starter, but its price is more expensive than that of a soft starter, and its structure is more complicated. The soft starter is used in the place where the voltage needs to be reduced to start and stop, and the motor speed remains unchanged at this time; but the frequency converter is mainly used for speed regulation and constant voltage, and the speed is determined by the frequency. The difference between the two is that the inverter can set the running frequency arbitrarily, but the soft starter only plays the role of soft start and soft stop.
1. Definition and function of soft starter.
The soft starter is connected in series between the power supply and the controlled motor, and the microcomputer controls its internal thyristor to trigger the conduction angle to realize AC voltage regulation, so that the input voltage of the motor rises gradually from zero with a preset function until the end of the start. The full voltage of the motor is soft start. During the soft start process, the starting torque of the motor increases gradually, and the speed gradually increases until the thyristor is fully turned on. The motor works on the mechanical characteristics of the rated voltage, achieving smooth start and reducing the starting current. . Avoid initiating an overcurrent trip. When the motor reaches the rated number of revolutions, the starting process ends, and the rated voltage is provided for the normal operation of the motor. The soft starter (soft starter) is a novel motor control device that integrates motor soft start, soft stop, light load energy saving and multiple protection functions. It is called Soft Starter abroad. The soft starter uses three-phase parallel thyristors as voltage regulators, which are connected between the power supply and the motor stator. Such a circuit is a three-phase fully controlled bridge rectifier circuit. When using a soft starter to start the motor, the output voltage of the thyristor gradually increases, and the motor gradually accelerates until the thyristor is fully turned on, and the motor works on the mechanical characteristics of the rated voltage to achieve smooth start, reduce the starting current, and avoid starting overcurrent tripping. When the motor reaches the rated number of revolutions, the starting process is over, and the soft starter automatically replaces the thyristor that has completed the task with a bypass contactor to provide the rated voltage for the normal operation of the motor, so as to reduce the heat loss of the thyristor and prolong the service life of the soft starter , improve its work efficiency, and avoid harmonic pollution to the power grid. The soft starter also provides a soft stop function. The soft stop is the opposite of the soft start process. The voltage is gradually reduced, and the number of revolutions is gradually reduced to zero, so as to avoid the torque impact caused by free stop.
2. Definition and function of inverter.
A converter that converts alternating current with constant voltage and frequency into alternating current with variable voltage and frequency is called a frequency converter. Reduce the impact load caused by the motor startup, control the motor speed, lengthen the startup time, smooth the current, achieve the purpose of soft start, and at the same time improve the efficiency of the power grid and the motor. In fact, the frequency converter is mainly used in energy saving, through adjustment, the output voltage, current and frequency can be changed. Generally, the motor with adjustable speed uses a frequency converter.
3. The working principle of the inverter.
The frequency converter is a device that transforms the power frequency power supply (50Hz or 60Hz) into AC power supply of various frequencies to realize the variable speed operation of the motor. Among them, the control circuit completes the control of the main circuit, the rectifier circuit converts AC power into DC power, the DC intermediate circuit smoothes and filters the output of the rectifier circuit, and the inverter circuit reverses the DC power into AC power (and the core control circuit realizes: AC- straight-to-intersect process). The frequency conversion technology was born in response to the need for stepless speed regulation of AC motors.
Sollant Focus on Energy Saving